The present invention relates to a bearing for refrigerating compressor and to a refrigerating compressor.
CFC (chlorofluorocarbon) and HCFC (hydrochlorofluorocarbon) have been used as refrigerants for refrigerating compressor. Recently, however, in order to prevent destruction of ozone layer by chlorine contained in CFC and HCFC, HFC (hydrofluorocarbon) not containing chlorine has come to be used as a substitute refrigerant.
As the refrigerants is changed, it becomes necessary to change the material of the bearing for the refrigerating compressor, since HFC as the substitute refrigerant apt to cause corrosion of a material containing Al (aluminum) which has been used for the bearing. Accordingly, use of a material containing bronze, for example, has been studied as the material of the bearing. Japanese Patent Laying-Open No. 59-194128, for example, discloses a technique using a material containing bronze for the bearing.
The above described Laid-Open Application discloses a bearing for a refrigerating compressor in which a porous bronze based alloy impregnated with a compound substance including synthetic resin and lubricant is formed sintered on a backing metal. The bearing is so formed that both the porous bronze based alloy and the compound substance are sparsely exposed at a contact face with the shaft.
The aforementioned Laid-Open Application, however, does not at all disclose the ratio of exposure of the porous bronze based alloy at the surface to be in contact with the shaft. Therefore, the bearing in accordance with this application had the problem that seizure possibly occurs as sintering resistance lowers at the time of boundary lubrication, and that bearing clearance increases as the amount of wear increases by sliding, resulting in pries and seizure.
An object of the present invention is to provide a bearing for a refrigerating compressor having high seizure resistance at the time of boundary lubrication and small amount of wear caused by sliding, as well as to provide a refrigerating compressor including the same.
Through extensive study, the inventors have found that in a bearing for a refrigerating compressor, by changing the ratio of exposure of the porous bronze based alloy at the contact surface (sliding surface) with the shaft, seizure resistance and wear resistance can be changed. Further, the inventors have found that if the ratio of exposure is set within the prescribed range, a bearing satisfying both the wear resistance and seizure resistance appropriate for a bearing of a refrigerating compressor can be obtained.
Therefore, the bearing for a refrigerating compressor in accordance with the present invention includes a porous bronze based alloy and a resin material impregnated in pores of the porous bronze based alloy, wherein the porous bronze based alloy and the resin material are exposed at the sliding surface, with the ratio of the exposed area of the porous bronze based alloy at the sliding surface being at least 5% and at most 60%.
In the bearing for a refrigerating compressor in accordance with the present invention, the ratio of the exposed area of the porous bronze based alloy at the sliding surface is set to 5% to 60%, as the amount of wear caused by sliding is considerably large when the ratio is smaller than 5%, and seizure is likely as the seizure resistance extremely lowers when the ratio exceeds 60%. Accordingly, a bearing for a refrigerating compressor having high seizure resistance at the time of boundary lubrication, for example, and having small amount of wear caused by sliding can be obtained.
Porous bronze based alloy is used as it is not susceptible to corrosion caused by the substitute refrigerant, and seizure of the bearing can be avoided as the bronze based alloy has high thermal conductivity. Further, the bronze based alloy is made pores, since resin entering the pores establishes strong bond between the backing metal and the bronze based alloy, so that dropping of the bronze based alloy caused by wear at the time of sliding can be prevented. Further, resin material is used to prevent seizure, as seizure is likely when bronze based alloy alone is used.
Further, sparse exposure of the porous bronze based alloy and the resin material at the contact surface with the shaft is preferred. This allows as uniform as possible development of both the wear resistance of the bronze based alloy and the seizure resistance of the resin material.
In the present specification, the porous bronze based alloy refers to the porous bronze, which is an alloy of copper and tin, and it means not only the material formed solely of porous bronze but also a material containing not only the porous bronze but other elements.
In the bearing for a refrigerating compressor described above, the ratio of the exposed area of the porous bronze based alloy at the sliding surface should preferably be at least 5% and at most 30%.
The ratio of the exposed area of the porous bronze based alloy at the sliding surface is set to be at most 30%, as maximum effect of seizure resistance is attained in this range.
In the bearing for a refrigerating compressor described above, preferably, a backing metal is further provided, and the porous bronze based alloy and the resin material are formed on the backing metal.
Accordingly, as the resin enters the pores of the porous bronze based alloy, the bronze based alloy can be strongly bonded to the backing metal, and therefore dropping of the bronze based alloy caused by wear at the time of sliding can be prevented.
In the bearing for a refrigerating compressor described above, preferably, the refrigerant compressed by the refrigerating compressor is hydrofluorocarbon based substitute refrigerant not containing chlorine.
As the substitute refrigerant is used, destruction of ozone layer can be prevented, and the bearing in accordance with the present invention is hardly corroded even when the substitute refrigerant is used.
In the bearing for a refrigerating compressor described above, preferably, the resin material contains a compound substance including synthetic resin and the lubricant.
Therefore, the resin material can be appropriately selected dependent on the state of use.
In the bearing for a refrigerating compressor described above, the synthetic resin contains poly tetrafluoro ethylene, and the lubricant preferably contains lead.
Thus the material of the synthetic resin can be appropriately selected, and lead improves lubricancy.
In the bearing for a refrigerating compressor described above, preferably, the refrigerating compressor contains oleo polyacetal resin.
Accordingly, the resin material can be appropriately selected.
The refrigerating compressor in accordance with the present invention includes a scroll type compressing element having an orbiting scroll, a driving shaft for transmitting driving force to the orbiting scroll, and a bearing arranged at a portion which slides over the driving shaft, wherein the bearing includes porous bronze based alloy and resin material impregnated in the pores of the porous bronze based alloy, the porous bronze based alloy and the resin material being exposed at the sliding surface, with the area of exposure of the porous bronze based alloy at the sliding surface being at least 5% and at most 60%.
Thus, a refrigerating compressor including a bearing having high seizure resistance at the time of boundary lubrication or the like and small amount of wear caused by sliding can be obtained.
In the refrigerating compressor described above, the bearing is preferably a journal bearing arranged at a sliding portion where the orbiting scroll and the driving shaft slide over each other.
Therefore, at the sliding portion between the orbiting scroll and the driving shaft, seizure resistance at the time of boundary lubrication or the like can be improved, and the amount of wear caused by sliding can be reduced.
In the refrigerating compressor described above, the bearing is preferably a journal bearing arranged at the sliding portion between a housing and the driving shaft.
Thus, at the sliding portion between the housing and the driving shaft, seizure resistance at the time of boundary lubrication or the like can be improved, and the amount of wear caused by sliding can be reduced.
The refrigerating compressor described above preferably has a structure in which oil is supplied to the bearing through an oil feed inlet provided at the driving shaft.
As described above, the bearing used in the present invention has high seizure resistance and small amount of wear caused by sliding. Therefore, even when oil supply to the bearing portion becomes insufficient temporarily resulting in boundary lubrication, seizure and wear can be prevented, and therefore it is optimal for the refrigerating compressor having the above described oil feed path.